Olfactory regulation of mosquito-host interactions

Abstract

Mosquitoes that act as disease vectors rely upon olfactory cues to direct several important behaviors that are fundamentally involved in establishing their overall vectorial capacity. Of these, the propensity to select humans for blood feeding is arguably the most important of these olfactory driven behaviors in so far as it significantly contributes to the ability of these mosquitoes to transmit pathogens that cause diseases such as dengue, yellow fever and most significantly human malaria. Here, we review significant advances in behavioral, physiological and molecular investigations into mosquito host preference, with a particular emphasis on studies that have emerged in the post-genomic era that seek to combine these approaches.

Fig. 1

Schematic representation of the intracellular components of olfactory signal transduction pathways. Here, a 7 transmembrane odorant receptor protein (OR) lying within the ORN dendrite interacts directly with odorants or alternatively (?) in the context of odorant-binding protein (OBP) complexes. In both cases, subsequent interactions with heterotrimeric G-protein complexes (G/G′) activate downstream effector enzymes adenyl cyclase (AC) and phospholipase C (PLC). This leads to the synthesis of the second messengers cyclic AMP (cAMP), diacylglycerol (DAG) and inositol 1,4,5 triphosphate (IP₃) that regulate several cation (Na⁺, Ca⁺⁺) channels that carry the transduction current. In addition, OBPS are hypothesized (?) to interact with odorant degrading enzymes (ODEs) to clear unbound ligand from the extracellular space. Signaling is terminated (bulbed lines) by decoupling of OR/G-protein complexes by arrestins (A) and G-protein coupled receptor kinases (GRKs).